Combustion control apparatus



Nov. 5, 1957 'r. GRAY COMBUSTION CONTROL APPARATUS Filgd March 5, 1953 2 Sheets-Sheet 1 INVENTOR THOMAS GRAY.

%a% ATT R N EYS Nov. 5, 1957 T. GRAY 2,812,140

COMBUSTION CONTROL APPARATUS Filed March 5, 1953 2 Sheets-Sheet 2 6J 16 A i J g '65 aa ll$1 75 Z\"\ a9 c9] 6 25$ I U 74 v a 1 7; fq,

CGMBUSTION CONTROL APPARATUS Thomas Gray, Newcastle-upon-Tyne, England, assignor to C. A. Parsons & Company Limited, Newcastle-upon- Tyne, England Application March 5, 1953, Serial No. 3461523 Claims priority, application Great Britain March 25, 1952 6 Claims. (Cl. 236-'-15) This invention relates to combustion control apparatus in such systems as employ automatic ignition.

The advantages of automatic ignition are well known and the principle has been widely adopted although, hitherto, such systems have been mainly electrical.

The object of this invention is to provide an improved combustion control apparatus or systemwhich whilst giving automatic ignition is simple, robust and reliable, and provides adequate protection. This object I find can be attained by utilising a hydraulic ignition and protection system with certain qualifications as stated in the following paragraph, fuller protection being available in accordance with the second paragraph below.

The invention consists in combustion control apparatus comprising means wherein a temperature indicator is used in conjunction with a hydraulic relay system which system comprises a timing device, hydraulically operated to control fuel, air and electricity to a torch igniter or igniters, a servo device attached to or associated with the torch igniter which controls a fuel shutoff valve governing the supply of fuel to the main burner, or burners, and cutting off the fuel supply in the event of failure to ignite; a servo mechanism, coupled to the temperature indicating device, which controls a fuel throttle to restrict the flow of fuel to the burner or burners in the event of an excessive combustion chamber outlet temperature occurring, restricts theflow of fuel to the burner or burners when the rate of change of temperature rise is excessive, and also maintains the temperature at a given or preset level; and provides means whereby the fuel supply to the burner or burners is completely out off when the temperature rise across the combustion chamber, that is to say the temperature in the combustion chamber or the difference of temperature between incoming and outgoing products, falls below a given or preset value, that is to say it afiords protection against flame extinction.

1 Referring to the accompanying diagrammatic drawings:

Figure 1 shows a complete system as used with two or more combustion chambers;

' Figure 2 shows one form a timing device;

Figure 3 shows an alternate formof timing device;

Figure 4 shows a form of torch igniter;

Figure 5 shows a temperature responsive means and a control device adapted for use with two combustion chambers or more. 7

Referring now to the accompanying diagrammatic drawings; in Figure 1 two combustion chambers are indicated at' 1 and'Z, the directionof the air flow being shown by arrows.

Fuel is supplied to main fuel injectors 3 and 4 from fuel tank 5, through fuel pump 6, through hand control, speed control and other fuel valves indicated generally at 7, through a temperature limiting fuel throttle valve 8, fuel shut-off valve or valves 9, and finally a device 16} which may be any suitable device for dividing the flow of fuel in equal proportions.

The main fuel injectors 3 and 4 are ignited by torch igniters 11 and 12, operating in parallel and drawing their fuel supply by way of a separate fuel circuit from the main supply, although not necessarily from the high pressure side of the fuel pump, through pipe 13 to timing device 14, described in detail later and through pipes 15, 1.6 and 17 to the torch igniters.

A supply of high pressure air to the torch igniters is also indicated as coming from air pump 18, through pipe 19, through the timing device 14, and through pipes 20, 21 and 22 to the torch igniters.

An electric supply for sparking plugs 23 and 24 on the torch igniters is indicated at 25. The electric current passes through wire 26, through a switch on the timing device id to a voltage booster coil or coils, indicated at 27 and through wires 28 and 29 to the sparking plugs 23 and 24.

A control oil pump 3%) has its delivery maintained at constant pressure by relief valve 31. This pump supplies oil to control valves on the torch igniters 11 and 12, and temperature responsive means indicated generally at 32 and 33, thence through preset restrictions 34 and 35 to drain tank 36.

The components and operation will now be described with reference to the other diagrammatic drawings beginning with Figures 2 and 3.

The alternative forms of timing device shown in Figures 2 and 3 supply fuel, compressed air and electricity to the torch igniters.

A hand operated lever indicated at 37 has a fulcrum at 38 and is suitably coupled so that a movement of the lower end of the lever to the right moves plunger 39 and piston 4!? to the left against the action of spring 41. This action closes electrical contacts 42 and brings a passage 43 on plunger 39 into line with air inlet and outlet connections 44 and 45 to allow free passage of air from air compressor 18 to the torch igniters 11 and 12 of Figure 1. At the same time, in the case of the timer shown in Figure 2, this action brings a passage 46 into line with fuel inlet and outlet connections 47 and 48 to allow free passage of fuel from fuel supply 5 to the torch igniters ill and 12 of Figure 1. In Figure 2, a cylinder 49 is filled with control oil on both sides of the piston 46. Movement of the piston to the left opens a spring loaded non-return valve Sit and allows control oil to flow from the left to the right side of the piston. When the lever 37 is released the spring 41 urges the piston and plunger assembly'to the right allowing oil to flow through a restriction 51 from the right to the left side of the piston at a preset rate. When the piston has reached the end of its travel to the right the electrical contacts are broken and the fuel and air connections are covered by the plunger 39, thus electric supply, fuel and air are allowed to flow to the torch igniters for a preset'time as determined by the. timing cylinder 40, dimensions and characteristic of spring 41, piston 40 and restriction 51.

In Figure 3, fuel is employed as the timing fluid. A movement of the piston '40 to the left allows fuel to fiow into the cylinder 49 from the fuel'supply through a spring loaded non-return valve 52. When lever 37 is released the piston and plunger are urged to the right by spring 41. This action closes valve 52 and allows fuel to flow from the cylinder through spring loaded non-return valve 53 to the torch igniters.

An air connection 40a to the combustion chamber inlet maintains the pressure difference between fuel pressure in cylinder 49 and combustion chambers land 2 constant and independent of variations in combustion chamber air pressure. v w

Referring now to the torch igniter shown in Figure 4,

air enters at 54, part passing through swirl slots 55 to assist in the atomisation of the fuel, the remainder pass- "Patented Nov. '5, 1957' 3 ing through holes 56 into annular passage 57. The two air streams mix in conical part 58 before passing into the respective combustion chambers 1 and 2 to ignite the main fuel spray from injectors 3 and 4 respectively. Fuel enters through pipe 59 into fuel sprayer 60 which may be of either a pressure swirl type or air blast type depending upon the air and fuel pressures available. Fuel is sprayed into ignition space 61 and is ignited by spark plug 62. A simple control valve is indicated consisting of a piston 64 coupled to rod 65, the piston being free to slide in cylinder 63 under the action of the rod 65; control oil enters the cylinder at 66 and leaves through an annular slot 67 defined by an annular groove in the cylinder and the end of the piston. When the timing switch is operated, fuel, air and electricity are supplied to the torch igniter. Cone 58 expands relative to rod 65 which is preferably of the same material and coeflicient of ex pansion. This allows piston 64 to uncover port 67 allowing oil to flow through. If two or more igniters are in use, for example, when two or more combustion cham- 9 bers are being used, the control valve cylinders of each igniter are connected with their oil streams in series with an adjustable restriction which may be for example a needle valve 35 as shown in Figure 1, so that when both torch igniters are in operation oil is allowed to flow 0 through the said control devices thus raising the pressure at the point before the restriction which is connected to fuel shut-off valve 9, and allowing the valve to open.

Referring now to the temperature responsive means shown in Figure 5, these consist of three concentric tubes immersed in the combustion chamber outlet gas stream. Outer and inner tubes 68 and 69 are made from a high temperature metal having a high coeflicient of linear expansion while an intermediate tube 70 is made either from a metal having a low coeflicient of linear expansion or a non-metal such as silica which has a very low coefiicient. The three tubes are connected at their inner ends 71 so that any relative expansion due to a change in temperature takes place from this end. Air from the combustion chamber inlet passes through pipe 72 and through the inner tube 69. Thus relative expansion between the tubes 68 and 69 is proportional to the temperature rise across the combustion chambers 1 and 2 while relative expansion between tubes 68 and 70 is proportional to combustion chamber outlet temperature. If the tube 79 is made from a metal of low but appreciable coefficient of expansion but arranged to have a lower rate of heat transfer, anticipation or velocity feedback is obtained between tubes 68 and 70. Outer tube 68 is rigidly connected to frame 73 onwhich is mounted fulcrum bracket 74 and the control devices associated with the temperature responsive means. The control devices for maximum temperature control and ,for equal temperature control are incorporated in a single cylinder 75 whilst the control device responsive to combustion chamber temperature rise is incorporated in cylinder 76.

In cylinder 75 the control device for equal temperature control consists of a piston 77 which is pressed by a spring 78 into contact with a spindle 79 which is coupled through an adjustment 80 to piston 81, which is part of the control device for maximum temperature control to be described later, and also to lever 82. Movement of piston 77 and, of course, piston 81 is therefore proportional to the combustion chamber outlet temperature.

In cylinder 76 piston 83 is pressed by spring 84 into contact with lever 85 which is, in turn, in contact with the innermost tube 69. Movement of piston 83 is therefore responsive to combustion chamber temperature rise.

Considering first of all the control device in cylinder 76, port 86 is connected to a supply of control oil whilst port 87 is connected to drainthrough an adjustable restriction 35, the pressure at the upstream end of which is communicated to the fuel shut-off valve 9. As the temperature in the combustion chamber rises, tube 68 expands and the end remote from the control valve mechanisrn moves towards the left of Figure 5 and in view of the fact that tube 69 is rigidly attachedto it, there is a similar movement of this tube also. This movement releases the pressure on lever 85 and this enables spring 84 to take over, urging piston 83 towards the left, until the lever 85 again contacts the end of tube 69.

At a preset combustion chamber temperature rise, the movement of the pistonwill have been such that the oil fed to port 86 can escape from the cylinder via an outlet annulus through port 87 thus allowing oil to flow to fuel shut-off valve and raising the hydraulic pressure thereon was to maintain the valve in the open position. In the event of the flame in the combustion chamber being extinguished, the temperature in the combustion chamber will fall and the piston 83 will then move so as to cut off port 37, thus reducing the hydraulic pressure on valve 9 causing it to close and cut off the supply of fuel to the combustion chamber.

The control oil supply to this control device and to the control device on the igniter is through a parallel connection so that a flow of control oil from one or the other can keep the fuel shut-off valve open.

When two or more combustion chambers are in use the control device just described, namely that in cylinder 76, is connected in series with the corresponding control devices in the other combustion chambers so that if the flame is extinguished in any one combustion chamber the flow of control oil to fuel shut-off valve 9 is interrupted and the valve closes.

Coming now to the maximum temperature control device, port 88 is connected to a supply of control oil whilst port 89 is connected to drain through an adjustable restriction34, the pressure at the upstream end of which is communicated to fuel limiting throttle valve 8. At a predetermined temperature, piston 81 moves so as to allow the flow of control oil through ports 88 and 89. The resulting increase in pressure on the fuel limiting throttle valve 8 causes it to close partly, thus reducing the flow of fuel to the combustion chamber. If two or more combustion chambers are used, the control oil connections to each control device are in parallel with each other and in series with the restriction 34.

The control device for equal temperature control is only necessary when two or more combustion chambers are in use and in this device, piston 77 controls the flow of control oil through ports 90 and 91. Port 90 is connected to the oil supply whilst port 91 is connected to the port corresponding to inlet port 90 on the corresponding control device in the other combustion chamber, that is to say, the oil passages are in series with one another and with the drain For equal settings of the adjustment 80 the flow areas each of which has a restriction 91 will be equal and consequently the pressure drops through them will be equal. Thus the pressure in line 92 between pistons 77 on units 32 and 33 will be half the supply pressure for equal combustion chamber outlet temperatures. An indicator 93 is coupled to a differential piston 94 which has a 2:1 area ratio, the smaller area being connected to the oil supply while the larger area is coupled to pipe 92. When the pressure in pipe 92 is half of the supply pressure the differential piston is in balance while a change in this ratio causes the piston to move to operate the indicator 93 which may be of any convenient form and may be calibrated to indicate the extent of out of balance temperature. Piston 94 may be coupled to valve 10 by means of a duct 95 to restore equal temperatures.

The operation of the whole system is as follows:

Igniti0n.The fuel, air and control oil pumps are started. The lever on timing device 14 is actuated. This permits flow of fuel, air and electric current to the torch igniters 11 and 12. Ignition of the torch igniters operates the torch igniter control valve which opens the fuel shutoff valve 9.

Running-Fuel is sprayed from the main injectors 3 and 4. On ignition of the main sprays the temperature responsive units 32 and 33 indicate the rise in temperature across the combustion chambers and through the control devices associated therewith and a pressure is transmitted which retains the fuel shut-off valve open. The torch igniters cease operation at the end of the timing period as indicated by the timing device.

Prtecti0n.If the torch igniters fail to ignite the shutoif valve does not open and the timing device is returned for a restart at the end of the timing period.

If the torch igniters ignite the shut-off valve opens but if the main injectors fail to ignite the system is shut down and returned for a restart at the end of the timing period.

Excessive combustion chamber outlet temperatures either during starting or during normal running result in operation of the temperature responsive unit through the control devices associated therewith to partly close temperature limiting fuel throttle 8 to reduce the fuel flow and restore the temperature to its normal preset value.

Unequal combustion chamber outlet temperatures result in operation of the temperature responsive units through their control devices to operate the indicator 93.

The invention is not limited to either of the two forms of timing device illustrated, for instance if the quantity or pressure of fuel required by the torch igniters is such that it is inconvenient to operate the timer by hand, the operation may be performed by the servo oil by using a hand operated pilot valve.

The invention has been mainly described with reference to the industrial gas turbine but it may be applied to aircraft and marine gas turbines and to industrial furnaces and the like.

I find it desirable to provide protection against failure to ignite, protection against flame extinction, indication or protection or both against unequal gas outlet temperatures from the combustion chambers in those cases where several combustion chambers are employed in parallel, protection against excessively high gas outlet temperature from said combustion chamber and protection against too great a rate of temperature rise.

I claim:

1. In a combustion system having a combustion chamber, a fuel injecting means therein and automatic ignition means therefor, combustion control apparatus comprising means for supplying fuel to the combustion chamber through the said injecting means including a fuel supply line and a fuel limiting throttle valve and fuel shut off valve thereon, the said fuel shut off valve being yieldably urged toward shut off position, hydraulic means for holding the said shut off valve open, means for supplying fluid under hydraulic pressure to the last said means for holding the said shut off valve open and comprising two hydraulic control devices, one associated with the said ignition means within the said combustion chamber and the other with temperature responsive means situated in the combustion chamber outlet, said control device asscciated with the ignition means being responsive to the temperature of said means and said device associated with the temperature responsive means being responsive to the temperature rise in the combustion chamber, in such a Way that in the event of failure to ignite or extinction of the flame inside the combustion chamber they cause a reduction in hydraulic pressure on said fuel shut off valve so as to close it, the apparatus also including a second means for supplying fuel to the injecting ignition means and comprising a separate conduit including a timing valve arranged for opening to supply starting fuel to said ignition means, a timing device for closing the last said valve a predetermined time after the opening thereof, and a further control device associated with said temperature responsive means in the combustion chamber outlet and comprising means for applying hydraulic pressure to the said fuel limiting valve to regulate its opening, the last said control device being responsive to the temperature in the combustion chamber outlet for limiting the supply of fuel to the combustion chamber when either a predetermined temperature is exceeded or the rate of temperature rise exceeds a predetermined rate.

2. Combustion control apparatus as claimed in claim 1, in which the temperature responsive means comprise three concentric tubes, the inner and outer tubes of which are made of material having a coeflicient of linear expansion sufiicient to obtain a response in the control devices associated With such means, whilst the intermediate tube is made from material having a negligible coefiicient of linear expansion and a low rate of heat transfer, said tubes having one end immersed in the gas stream of the combustion chamber, which ends of the tubes are rigidly connected together, a support fixed with relation to the Wall of the combustion chamber attached to the other end of the outermost tube, levers in contact with the other ends of the innermost and intermediate tubes and movable thereby for operating the control devices associated with said temperature responsive means, and means for passing air or gas from the combustion chamber inlet through the innermost tube.

3. Combustion control apparatus as claimed in claim 2, in which the control device associated With the temperature responsive means for closing the fuel shut-off valve in the event of flame extinction in the combustion chamber, that is to say the control device response to combustion chamber temperature rise, comprises a piston, a cylinder having a plurality of ports for controlling the flow of control oil through the cylinder to the fuel shut off valve, a spring and lever yieldably urged thereby for moving the piston in the cylinder to cover and uncover the said ports, said lever being actuated by the innermost tube of the temperature responsive means in such a way that in the event of flame extinction in the combustion chamber the piston moves so as to close an inlet port for the control oil thus reducing the hydraulic pressure on the fuel shut-off valve so as to close it.

4. Combustion control apparatus as claimed in claim 2, in which the control device associated with the temperature responsive means for maximum temperature control comprises a piston moving in a cylinder under the action of a spring and a lever arranged so as to oppose one another, said piston covering and uncovering ports controlling the fiow of control oil, said lever being in contact with the intermediate tube of said temperature responsive means and causing the piston to move so as to permit the flow of control oil to the fuel limiting valve thereby increasing the pressure thereon and limiting the flow of fuel when the temperature in the combustion chamber reaches a predetermined maximum or the rate of temperature rise exceeds a predetermined value.

5. Combustion control apparatus as claimed in claim 1, in which the ignition means consist of an igniter supplied With air, electricity and fuel under the control of the timing device and the control device associated With said ignition means consists of a piston and rod coupled thereto, a cylinder attached to the side of the igniter, the piston being free to slide in the cylinder under the action of the rod means rigidly connecting the rod at its other end to the igniter outlet, such that when the igniter is lighted it expands relative to the rod causing the rod and hence the piston to move thereby opening ports in the cylinder and allowing control oil to flow through the cylinder and increase the pressure on the fuel shut-off valve so as to open it.

6. Combustion control apparatus as claimed in claim 1, in which the timing device comprises a plunger and piston having recesses and cooperating ports as hereinafter specified, a cylinder in which the piston moves containing control oil on both sides of the piston, a lever actuating said plunger and piston, movement of the lever causing electrical contacts to close supplying current to a sparking plug on the igniter and simultaneously moving the piston and plunger so that recesses on the plunger open fuel and air ports allowing said fuel and air to be communicated with the igniter, the piston moving against the action of a spring and oil flowing through a non-return valve on the piston head to the opposite side of the piston and such that when the lever is released the spring forces the piston and plunger back to their original position at a predetermined rate by allowing oil to be displaced back to the spring side of the piston by means of a restriction in the piston head, thereby breaking the electrical contacts and cutting off the fuel and air to the igniter.

References Cited in the file of this patent UNITED STATES PATENTS Hoff Aug. 17, 1926 Arnold Oct. 10, 1939 Allen Aug. 28, 1951 Goodwin Mar. 11, 1952 Ryder et al. May 13, 1952 Szydlowski Nov. 30, 1954 

